Management of Minor Elements

Management of Minor Management of Minor Elements in the Elements in the Production of Base MetalsProduction of Base Metals

Sharif Jahanshahi, Warren Bruckard, Chunlin Chen and Frank Jorgensen Mission: To progressively

eliminate waste and emissions in the minerals cycle, while

enhancing business performance and meeting community expectations

Presentation by Sharif Jahanshahi PhD, FAusIMM

Sharif Jahanshahi has over 30 years experience in R&D across; high temperature processing of ferrous and base metals, thermodynamics and kinetics of high temperature systems, melt chemistry, process modelling, simulation and development

Currently consulting for leading global players in the metallurgical industry through Meta-Logical Solutions Pty Ltd.

Website: http://www.metalogical.solutionsEmail: [email protected]

http://www.metalogical.solutions/

Green Processing 2006: 5-6 June 3

BackgroundBackground

Australia exports ~ 3 millions of tpa of copper, nickel, lead and zinc in form of concentrate and refined metals.

Base metal ores contain low levels (1- 104 ppm) of toxic/ hazardous elements (As, Sb, Bi, Cd, Hg, Se, Te…, Th, U)

Clean, coarsely-grained ore bodies becoming depleted

Ore bodies of future becoming more complex, finer-grained and containing higher amount of minor/toxic elements.

Worldwide industry mines and process 100s million tonnes of base metal ores each year

Accumulated mass of minor elements in biosphere is large and could have a significant environmental impact


Industry ContextIndustry Context

Minor elements present technical and environmental problems as well as being costly

Smelters impose treatment charges and penalty payment on minor elements in concentrates

Governments becoming increasingly sensitive to emissions

Community pressure for more sustainable processing

Smelters setting tighter penalty specifications for minor elements

Imperative to develop alternative treatments for selective removal of toxic elements at the mine site before despatch of concentrate to smelters


Options for Dealing with Toxic Options for Dealing with Toxic Elements in OresElements in Ores

Primarily determined by mineralogy and grain size

Occurrence - association with other elements

Distribution between phases

For widely and uniformly dispersed minor elements in mineral phases treatment option is limited

Separation and removal in waste/residue streams produced in metal extraction

If concentrated in discrete phases, options exists for early removal by physical and chemical means

Having separated and concentrated the toxic elements, consideration has to be given to their use or safe disposal


ArsenicArsenic

Is one impurity element found in most base metal ores and concentrates

Lowers metal quality, if not removed from product metal

Contributes to health concerns during metallurgical processing

Causes environmental concerns during disposal of tailings and wastes

High arsenic levels in an ore can make the deposit economically unviable

Blending of high and low arsenic concentrates has been practiced by industry. Can we continue this in the future?


Mineralogy Consideration Mineralogy Consideration

In copper ores arsenic occurs asEnargite (Cu3AsS4) Tennanite (3Cu2S.As2S3)

Arsenopyrite (FeAsS) Cobaltite (CoAsS)

In nickel systemsGersdorffite (NiAsS) Niccolite (NiAs)

Arsenopyrite (FeAsS) Cobaltite (CoAsS)

Physical separation of arsenic bearing minerals from non-arsenic bearing minerals is difficult Similar specific gravity, non-magnetic, strongly floatable with

conventional collectors etc.

Some As minerals contain high concentration of copper and nickel e.g. enargite (Cu3AsS4) has 48% Cu


Mineral Recovery in 1 minuteMineral Recovery in 1 minute

0

10

20

30

40

50

60

70

80

90

100

-500 -400 -300 -200 -100 0 100 200 300 400 500

Pulp potential (mV vs SHE)

Min

eral

rec

ove

ry a

t 1

min

(%

) Enargite (pH 8)

Chalcopyrite (pH 8)

0

10

20

30

40

50

60

70

80

90

100

-500 -400 -300 -200 -100 0 100 200 300 400 500

Pulp potential (mV vs SHE)

Min

eral

rec

ove

ry a

t 1

min

(%

) Enargite (pH 8)

Chalcopyrite (pH 8)

Senior et al J. Min Eng. Int, In press


Selective RoastingSelective Roasting

Roasting has been used to remove arsenic from ores and concentrates

A number of treatment options have been developed and reviewed in literature

Operating windows for selective removal of arsenic from copper concentrates identified through thermodynamic modelling


Effect of Roasting Temperature Effect of Roasting Temperature

100

80

60

40

20

0

500 600 700 800 900

Temp. (°C)

Rem

ova

l o

f A

rsen

ic (

%)

0.055%As

0.54%As

5.3%As

O2:Chalcopyrite = 2 CuFeS2:FeS2: FeS ~ 10:1.7:1

58% desulfurisation

100

80

60

40

20

0

500 600 700 800 900

Temp. (°C)

Rem

ova

l o

f A

rsen

ic (

%)

0.055%As

0.54%As

5.3%As

O2:Chalcopyrite = 2 CuFeS2:FeS2: FeS ~ 10:1.7:1

58% desulfurisation

Nakazawa, Yazawa & Jorgensen Met Trans 30B, 1999


Effect of Oxygen Supply at 700 CEffect of Oxygen Supply at 700 C

100

80

40

60

20

01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

O2 : chalcopyrite (mol:mol)

Re

mo

val

of

Ars

en

ic (

%)

5.3% As

0.54% As

0.055% As

700 ° C

FeAsO4

100

80

40

60

20

01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5


Re

mo

val

of

Ars

en

ic (

%)

5.3% As

0.54% As

0.055% As

700 ° C

FeAsO4



Effect of Oxygen Supply at 900 CEffect of Oxygen Supply at 900 C

100

80

40

60

20

01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5


Re

mo

val

of

Ars

en

ic (

%)

5.3% As

0.54%

0.055%

900 °C

100

80

40

60

20

01.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5


Re

mo

val

of

Ars

en

ic (

%)

5.3% As

0.54%

0.055%

900 °C



Arsenic Removal from Copper Arsenic Removal from Copper Concentrate during RoastingConcentrate during Roasting

Smelter Roaster* Temp.(°C)

Arsenic in feed

(wt %)

Arsenic removal

(%)

Sulphur removal

(%)

US EPA MH 540 0.2 27 -

US EPA FB 540 to 620 0.02 15 -

El Indio MH 720 max. 6.4 >90 56

Saganoseki FB 685 to 705 5 to 6 85 to 90 60 to 70

Lepanto FB 700 1.3 82 60

Oroya MH 700 2.6 76 53

Boliden FB 700 to 720 2 92 56

*MH = multi-hearth and FB = fluidized bed


Distribution of As, Bi, Pb during Distribution of As, Bi, Pb during SmeltingSmelting

40 45 50 55 600

25

50

75

100T=1573 KPSO2=0.1 atmIron silicate slag

bBi

Gas

Matte

40 45 50 55 600

25

50

75

100T=1573 KPSO

2=0.1 atm

Calcium ferrite slag

T=1573 KPSO

2=0.1 atm

Calcium ferrite slag

eBi

Gas

Matte

wt% Cu in matte

40 45 50 55 600

25

50

75

100T=1573 KPSO

2=0.1 atm

Iron silicate slag

aAs

Slag

Gas

Matte

Dis

trib

utio

n (

%)

40 45 50 55 600

25

50

75

100T=1573 KPSO2=0.1 atmCalcium ferrite slag

d

Matte

As

Slag

Gas

Dis

trib

utio

n (

%)

wt% Cu in matte

40 45 50 55 600

25

50

75

100cT=1573 K

PSO2=0.1 atm

Iron silicate slag

Pb

Gas

Matte

40 45 50 55 600

20

40

60

80

100

fPb

Gas

Matte

wt% Cu in matte

Chen et al Sohn Intl Symp , 2006


Simulated FlowsheetSimulated Flowsheet

Converting1st & 2nd Stages

Smelting

Fire-refining1st & 2nd Stages

CopperConc

Slag

Slag

Matte

Blister Copper

Anode Copper

Gas

Gas

Gas

Air + Flux

Air + Flux

Air/Methane


Arsenic Distribution Arsenic Distribution - - From Concentrate to Anode CopperFrom Concentrate to Anode Copper

0

25

50

75

100

Smelting Convert 1 Convert 2 Fire-ref 1 Fire-ref 2

Processing Step

Ars

en

ic D

istr

ibu

tion

(%

)

Gas

Slag

Matte/ Copper0.1 wt% As in Conc

Iron silicate slag


Arsenic Deportment Arsenic Deportment - From Concentrate to Anode Copper- From Concentrate to Anode Copper

0

25

50

75

100

Smelting Convert 1 Convert 2 Fire-ref 1 Fire-ref 2

Processing Step

Ars

en

ic D

ep

ort

me

nt (

wt%

)

Gas

Slag

Matte/Copper

0.1 wt % As in ConcIron silicate slag


Copper Production from Sulfide Copper Production from Sulfide OresOres

Ore

Tailing Dam

Anode Slimes

Smelting

Air, Flux, Coal Air, Flux

Acid Plant

Concentrate Matte Blister

AnodeCopperr Copper

99.99%

AnodeSlimes

Air, Natural Gas

Air, Flux

Slag

SlagSlagSlag

Acid

Dore Metal (Ag-Au)

Tailings

Gypsum

Tailing Dam

Tailing Dam

Flotation Smelting 2-stage Converting

Fire-refining Electro-refining


Safe Disposal of Toxic ElementsSafe Disposal of Toxic Elements

Production of arsenic and other toxic elements is well in excess of market demand

Typically concentrated in form of fumes, dross, precipitates and slags

Disposal of surplus in a safe and environmentally acceptable manner

Thus conversion to a less hazardous form and longer term solutions are required conversion into calcium arsenate, ferric arsenate etc.

encapsulation in concrete or locking in silicate slags

Careful assessment of these options is required


The Early Removal OptionsThe Early Removal Options

TailingDam

Flotation

Roaster

Smelter

Low As Conc

High AsConc

Low AsConc

Safe Disposal e.g mine backfill

Ore

Arsenic Fumes


ConclusionsConclusions

Increasing pressure on metal producers to reduce emissions and manage toxic elements deportment

Challenge - orebodies with higher levels of minor elements, which are difficult to process

Early removal option offers competitive advantage

Several options for safe disposal of low volume highly toxic streams, which could be linked with the early removal

We believe, it is time to put current capability into practice by examining the integrated flowsheets to deal with the management of the minor elements in a more sustainable way.


AcknowledgementAcknowledgement

Some of the work and findings presented were generated

through a project carried out under the auspice and

financial support of the Cooperative Research Centre for

Sustainable Resource Processing, which was established

and is supported under the Australian Government's

Cooperative Research Centres Program

Management of Minor Elements

Environment

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